Acquirer Reference Number
What is an acquirer reference number (ARN)?
Acquirer reference number (ARN) is a unique identifier assigned to a card transaction by the or as the payment moves from the merchant's bank, through the , to the cardholder's . It gives every party a single code to trace one specific transaction.
The issuer receives the ARN in the clearing messages sent by the acquirer once an authorized transaction has been confirmed at . From that point, merchants, issuers, and card networks all reference the same code to locate and investigate that exact payment. An ARN is sometimes confused with the : both are transaction trace identifiers, but an RRN is created at authorization, while an ARN is assigned later, during clearing and settlement.
Key facts about an ARN
An ARN is typically a 23-digit code, though its length can range from 8 to 30 characters depending on the card network. Rather than a random string, it packs structured information into a fixed format:
- Interchange Rate Indicator (IRI), reflecting the interchange calculation rules applied
- Acquirer Bank Identification Number (BIN)
- Processing date, written in Julian date format (the day of the year)
- Item sequence number, assigned by the acquirer to identify the transaction
- Check digit, used to validate the code the same way a card number is validated
The processing date is tied to the original transaction date and can't fall more than 30 calendar days after it, per card network rules. Because the final digit is a check digit, an ARN that's been mistyped fails validation, so an invalid-looking code is often just a transcription error.
How an ARN works
- A cardholder's payment is authorized by the issuer.
- The acquirer or processor batches the authorized transaction for clearing and assigns it an ARN.
- The ARN travels with the transaction through the card network to the issuing bank inside the clearing and settlement messages.
- Each party stores the ARN against its own record of the transaction.
- When that payment needs to be traced later, the ARN points every party to the same transaction.
Both online and offline transactions generate ARNs, so the same tracing method works across payment channels.
Where to find an ARN
- Merchant: the ARN appears in the payment processor or PSP reporting against the relevant order or payout, usually after the transaction settles.
- Cardholder: it isn't printed on a card statement. A cardholder who needs it contacts their bank, which can use the ARN to trace a payment or a refund.
- Developer: it surfaces in the transaction record returned by the processor or PSP, typically once the transaction reaches the clearing and settlement stage rather than at authorization.
Why an ARN matters
The ARN is what makes a single transaction findable once it has left authorization and entered clearing.
- For disputes and , the ARN identifies the precise transaction in question, which speeds up retrieval of its details.
- For refunds, it lets a cardholder's bank confirm whether and when a refund was actually processed.
- For , it gives finance teams a shared reference to match one payment across the acquirer, network, and issuer.
